Mathematical models have been developed for describing the dynamical events which occur on the lymphocyte plasma membrane subsequent to interaction with antigen. The models have been simulated numerically in an attempt to understand whether these events are important in the control of the quality of antibody (i.e. affinity) produced during a response, and if so, how they exert their influence. BIBLIOGRAPHIC REFERENCES: DeLisi, C. and Perelson, A.: Kinetics of aggregation phenomona. I. Minimal Models for Patch Formation on Lymphocyte Membranes. J. Theor. Biol. 62: 159-210, 1976. DeLisi, C.: Physical Chemical Aspects of Cellular Selection in an Immune Response. In Bell, G.I. (Ed.): Theoretical Immunology. New York, Marcel Dekker, 1977, In press.